<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>计算器</title>
</head>

<body>

    <div id="app">
       <div class="input-num">
            <button @click="sub">
                -
            </button>
            <span>{{num}}</span>
            <button @click="add">
                +
            </button>
       </div>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    <script>
        var app = new Vue({
            el: "#app",
            data: {
                num:1
            },
            methods:{
                add:function(){
                    // console.log('add');
                    if(this.num<10){
                    this.num++;
                    }else{
                        alert('最大值了')
                    }
                },
                sub:function(){
                    // console.log('sub');
                    if(this.num>0){
                    this.num--;
                    }else{
                        alert('最小值了')
                    }
                },
            }
        })
    </script>
</body>

</html>